AMEGHINIANA (Rev. Asoc. Paleontol. Argent.) - 47 (3): 387-400. Buenos Aires, 30-09-2010 ISSN 0002-7014

Predation bite-marks on a peirosaurid crocodyliform from the Upper Cretaceous of Neuquén Province, Argentina

Lucas Ernesto FIORELLI1

Abstract. Bite marks and injuries caused by intraspecific predation or aggressive social behavior are un- common in fossil vertebrates, and in the fossil record of suchian archosaurs they are extremely unusual. A peirosaurid crocodyliform collected from the Upper Cretaceous beds of the Neuquén Group (northern Patagonia, Argentina) shows abundant bite marks and injuries. These injuries are spread across all the preserved parts of the specimen, with the highest concentration of bite marks, perforations and breakage in the caudal region. Characteristics of these injuries are analyzed, and their possible origin and related taphonomic aspects are assessed. Results indicate that the injuries were not produced by intraspecific figh- ting, but probably by the predating action of a theropod dinosaur. Resumen. MARCAS DE PREDACIÓN EN UN CROCODILIFORME PEIROSAURIDO DEL CRETÁCICO SUPERIOR DEL NEU- QUÉN, ARGENTINA. El hallazgo de marcas de mordeduras y lesiones por predación o comportamiento so- cial agresivo intraespecífico en vertebrados fósiles es poco frecuente. En el registro fósil de arcosaurios su- quianos tales evidencias son extraordinarias. Aquí se reporta un crocodiliforme peirosáurido del Cretácico Superior del Grupo Neuquén (norte de Patagonia, Argentina) con abundantes marcas de mordeduras y lesiones. Estas heridas están localizadas en todas las partes preservadas del espécimen, con una alta con- centración de mordeduras, perforaciones y roturas en la región caudal. En el presente trabajo, se analizan las características de las lesiones, y también sus posibles causas y los aspectos tafonómicos relacionados. Los resultados muestran que las mordeduras fueron hechas por la acción de un predador y no por peleas intraespecíficas.

Key words. Bite marks. Predation. Peirosaurid. Upper Cretaceous. Neuquén. Palabras clave. Mordeduras. Predación. Peirosáurido. Cretácico Superior. Neuquén.

Introduction specimen of the crocodyliform Baurusuchus pachecoi Price, 1945, from the Adamantina Formation, Bauru Bite marks and injuries produced by predation Basin (Brazil), was recently reported (Avila et al., and scavenging in vertebrate fossils are uncommon 2004). These authors argued that such bite marks and only a few cases are well documented (Erick- were produced by cospecific combat. son and Olson, 1996; Chure et al., 1998; Frey et al., Ethology and social behavior of extant crocody- 2002; Everhart, 2005; Reisz and Tsuji, 2006; Bianucci lians is more complex than that of other non-archo- et al., 2010; Hone et al., 2010). Even less common are saurian reptiles (Avila et al., 2004). Many ethologi- cases in which the bite injuries are caused by intras- cal traits, a combination of sensory signals (olfac- pecific and cofamilial aggressive social behavior tory, visual, and acoustic), and several corporal (Molnar and Farlow, 1990; Sereno and Novas, 1993; postures and social displays are used as warnings Tanke and Currie, 1998; Bell and Currie, 2009). Ca- before escalation to physical intraspecific aggres- ses applicable to crocodylomorphs are also limited, sion occurs (Hunt, 1977; Garrick et al., 1978; Vliet, with only a few examples recorded in fossil mem- 1989; Thorbjarnarson and Hernández, 1993; Pough bers of this group (Gilmore, 1946; Buffetaut, 1983; et al., 1998; Senter, 2008). Injuries are caused fre- Sawyer and Erickson, 1998; Frey et al., 2002). A case quently when for some reason —e.g., disputes for of injuries and bite marks produced on the tail of a food or territory, dominance fights during repro- ductive period and courtship behavior, etc.— figh- ting takes place (Cott, 1961; Hunt, 1977; Vliet, 1989, 2001a, 2001b; Senter, 2008). Adult or subadult ex- 1Centro Regional de Investigaciones Científicas y Transferencia tant crocodilians have virtually no natural preda- Tecnológica de La Rioja, Entre Ríos y Mendoza s/n, 5301 Anillaco, tors. However, crocodilian nests, neonates and ju- La Rioja, Argentina. [email protected] veniles are predated by mammals, birds, fishes, ©Asociación Paleontológica Argentina AMGHB2-0002-7014/10$00.00+.50 388 L.E. Fiorelli snakes, turtles, and even other crocodilians (Scott, arid and dry continental climate was dominated by 2004). As adult members of this group represent the aeolian deposition, creating big dunes and inter-du- top predators in their trophic environments, cases ne lagoon basins skirted by fluvial deposits, criss- in which they have been attacked by other preda- crossed by streams and seasonal or ephemeral wa- tors have been very rarely recorded. ter bodies. The horizon in which the fossil was Herein I report a peirosaurid crocodyliform from found is composed of coarse-grained, light violet to the Santonian Bajo de la Carpa Formation in Neu- pink sandstones of fluvial origin. quén Province, Argentina (Bonaparte, 1991; Fiorelli et al., 2007), with numerous injuries, perforations, breakage, and bite marks. These injuries are present Fauna of the Bajo de la Carpa Formation throughout most of the preserved parts of the speci- men being more frequent in the caudal section. Various outcrops of the Bajo de la Carpa For- mation have yielded a rich fossil vertebrate assem- blage (figure 2.2), including the remains of an inde- Material and methods terminate titanosaurid (Chiappe and Calvo, 1994; Parras and González Riga, 2001), cf. Laplatasaurus The specimen described here, MUCPv-27 (figure Huene, 1929 (Leanza et al., 2004), and the peculiar 1.1-1.8), represents a new species of a still unnamed beaked sauropod Bonitasaura salgadoi Apesteguía, peirosaurid crocodyliform (Fiorelli et al., 2007). 2004, found at the locality known as La Bonita, in Río Bonaparte (1991) briefly described this specimen and Negro Province. The theropod dinosaur fauna is al- suggested that it would represent a taxon closely re- so diverse, including the small abelisauroid thero- lated to Araripesuchus Price, 1959. Nevertheless, a re- pod Velocisaurus unicus Bonaparte, 1991, found in cent review of MUCPv-27 stated that it would not re- Neuquén (also in the Campus of the University of present a form closely related to the Notosuchia, but Comahue). Recently, the presence of carnotaurine instead exhibits affinities with neosuchian peirosau- abelisaurid theropods was reported from the top of rids (Fiorelli et al., 2007). Available fragmentary re- the unit in the La Invernada region , in northern mains include many elements in good state of pre- Neuquén (Porfiri and Calvo, 2006), and also at Paso servation but most of the fossil was lost (probably Córdova (Río Negro Province) (Ezcurra and owing to predation). Preserved elements of MUCPv- Méndez, 2009). Aditionaly, remains of indetermina- 27 (figure 1.1-1.8) include cranial remains, nine dor- te theropods coming from the Auca Mahuida region sal vertebrae, some articulated appendicular ele- (Neuquén Province) were considered by Coria and ments, numerous presacral osteoderms, and an al- Arcucci (2004) to be large basal tetanurans related to most complete caudal region that is fully enclosed by carcharodontosaurids. Porfiri et al. (2008) reported osteoderms. Materials were photographed, drawn, from Tratayén (Neuquén Province) an articulated and different digital programs were used for the postcranium belonging to an allosauroid related to analysis and design of the images and to highlight the Carcharodontosauria (sensu Benson et al., 2009). specific anatomical aspects. Coelurosaurian dinosaurs are also common and re- latively well-known, such as the alvarezsaurids Abbreviations. MUCP, Museo de Geología y Paleontología, Alvarezsaurus calvoi Bonaparte, 1991 (Campus of the Universidad Nacional del Comahue, Neuquén, Argentina. University of Comahue) and Achillesaurus manazzo- MUCPv-27 is currently housed at the Centro Paleontológico Lago Barreales -CePaLB-, State Route #51, Km 65, Neuquén Province, nei Martinelli and Vera, 2007 (Paso Córdova), the Argentina. enantiornithine Neuquenornis volans Chiappe and Calvo, 1994, and the basal ornithuromorph Patagopteryx deferrariisi Alvarenga and Bonaparte, Locality and horizon 1992 (both in the Campus of the University of Comahue). Also, bird egg-clutches with embryos Specimen MUCPv-27 comes from beds exposed (Schweitzer et al., 2002) (Campus of the University of within the Campus of the University of Comahue, Comahue), dinosaur eggs related to Megaloolithus pa- in the city of Neuquén (38º56’25”S - 68º3’10”W) (fi- tagonicus Calvo et al., 1997 (south of Neuquén city), gure 2.1). In this area, the outcrops are referred to and remains of the snake Dinilysia patagonica Wood- the Bajo de la Carpa Formation, Río Colorado ward, 1901 (Campus of the University of Comahue). Subgroup, Neuquén Group (middle-upper In addition, the chelid Lomalatachelys neuquina Lap- Santonian; Leanza et al., 2004) (figure 2.2). Unlike ot- parent de Broin and de la Fuente, 2001, comes from her sections in the basin, the rocks of this formation Loma de la Lata, in Neuquén Province (de la Fuente, in the city of Neuquén were deposited in fluvial and 2007) and constitutes a common faunal element. aeolian systems (Sánchez et al., 2006). Moreover, the Crocodyliforms are an important faunal compo- AMEGHINIANA 47 (3), 2010 Predation on a Cretaceous peirosaurid crocodyliform 389

Figure 1. Some elements of the MUCPv-27 peirosaurid. 1 and 2, caudal vertebrae in right lateral (1) and posterior (2) views; 3, several armor pieces, osteodermal plates of the trunk and ribs fragments; 4, fragment of the snout showing both nasals; 5, dorsal vertebra; 6, ar- ticulated middle dorsal vertebrae and plates; 7, indeterminate appendicular elements; 8, very complete caudal region showing disposi- tion of the armor on the tail / algunos elementos del peirosaurido MUCPv-27 1 y 2, vértebra caudal en vista lateral derecha (1) y posterior (2); 3, varias piezas de la dermostea, osteodermos del tronco y restos de costillas; 4, fragmento del hocico mostrando ambos nasales; 5, vértebra dorsal; 6, vér- tebras dorsales medias y placas articuladas; 7, elementos apendiculares indeterminados; 8, región caudal muy completa mostrando la disposición de la dermostea sobre la cola. nent of the Bajo de la Carpa Formation with Noto- Brief description of MUCPv-27 suchus terrestris Woodward, 1896, being the most abundant vertebrate from the unit (remains of No- The elongated nasals form the dorsal edge of the tosuchus were found in the Campus of the Uni- external nares and bear deep pits and grooves re- versity and at Paso Córdova). Other crocodyli- sembling those of peirosaurids. The median suture is forms, found in the Campus of the University and evident and straight. The lateral edges of the nasals at Paso Córdova, are the derived notosuchian Co- are subparallel to each other. As in other peirosau- mahuesuchus brachybuccalis Bonaparte, 1991 (Cam- rids, the internal surface does not bear a nasal sep- pus of the University), the baurusuchids Cyno- tum (figure 1.4). dontosuchus rothi Woodward, 1896 (uncertain loca- The degree of preservation of some of the post- lity), Wargosuchus australis Martinelli and Pais, cranial materials is exceptional, as most of the osteo- 2008, and the basal mesoeucrocodylian Neuquen- derms are preserved in natural articulation (figures suchus universitas Fiorelli and Calvo, 2007, the last 1.6, 3.1-3.3). The dorsal region of the vertebral co- two from the Campus of the University of Co- lumn is short and represented by nine elements, four mahue. of which are articulated to each other and to several AMEGHINIANA 47 (3), 2010 390 L.E. Fiorelli

AMEGHINIANA 47 (3), 2010 Predation on a Cretaceous peirosaurid crocodyliform 391 ventral groove on the centra, like other peirosaurids (Fiorelli et al., 2007). The external surfaces of the osteoderms are hea- vily ornamented by deep pits and grooves and bear a slightly developed ridge (figures 1.3, 1.6). In MUCPv-27 the dorsal osteoderms of the first para- vertebral row possess rounded lateral edges (figure 1.6). This character differs from that of other peiro- saurids that possess dorsal osteoderms with straight lateral edges (e.g., Uberabasuchus Carvalho et al., 2004). The presacral dorsal osteoderms are preserved in na- tural articulation, indicating the presence of a single row of parasagittal osteoderms flanked by accessory (rounded) osteoderms (figure 1.3). This morphology contrasts with that of other peirosaurids (e.g., Maha- jangasuchus Buckley and Brochu, 1999, and Ubera- basuchus Carvalho et al., 2004), suggesting that this poorly studied clade had a highly diversified osteo- derm morphology and arrangement. Numerous

Figure 3. Dorsal vertebrae and articulated trunk osteoderms of the small osteoderms with complex articulated edges re- MUCPv-27 peirosaurid showing several bite marks. 1, left lateral present elements of the ventral armor (figure 1.3). view; 2, dorsal view; 3, ventral view. The black and white arrows The caudal osteoderms completely enclose the tail indicate puncture marks and injuries present in the specimen / endoskeleton; their general morphology varies accor- vértebras dorsales y osteodermos articulados del tronco del peirosáurido MUCPv-27 mostrando diversas marcas de mordedura. 1, vista lateral; 2, ding to their location, ranging proximo-distally from vista dorsal; 3, vista ventral. Las flechas negras y blancas indican las subquadrangular to anteroposteriorly elongated ele- marcas de perforaciones y lesiones presentes en el espécimen. ments (figure 1.8). paravertebral dorsal osteoderms. Seven dorsal ver- Bite marks in the peirosaurid MUCPv-27 tebrae lack their centra whereas the other two dorsal vertebrae have complete spool-shaped centra with a Virtually all the preserved elements of MUCPv- completely closed neurocentral suture. Brochu 27 carry clear signs of injury and bite marks, (1996) showed that neurocentral sutures in the ex- mainly in the osteoderms and vertebrae that com- tant crocodylian vertebral column close in a poste- pose the caudal section (figure 1.8). More than 70 rior-anterior pattern as the animal matures. bite marks, punctures, breakage points, and other Moreover, this author used these ontogenetic chan- related damage are present in the preserved parts ges as relative maturity indicators (Brochu, 1996). of the specimen. All marks are in the postcranial This pattern was recently confirmed as plesiomorp- area, which is not surprising due to their fragmen- hic for the Pseudosuchia (Irmis, 2007). Although it is tary nature and the lack of preservation of more impossible to pinpoint the age of the MUCPv-27 pei- skull material. rosaurid (due to lack of histological data), the neu- The articulated dorsal section presents some in- rocentral suture closure of the dorsal series could in- dications of bite marks and represents a very affec- dicate that it was a subadult or adult specimen. ted and damaged section. It cannot be established These vertebrae are robust, with anteroposteriorly whether this damage was due to predation or to la- elongated neural spines, and pre- and post-spinal la- ter erosion, although the biostratinomic processes minae. Caudal vertebrae (figures 1.1-1.2) possess affecting the material were more important than dorsally elongated neural spines, a noticeable deve- either the diagenetic or erosional processes (see be- lopment of the pre- and post-spinal laminae, and a low, Taphonomic Considerations). In any case, the

Figure 2. Locality and horizon. 1, map of Argentina and the Comahue region showing the site where MUCPv-27 was collected; 2, stra- tigraphic column of the Bajo de la Carpa Formation, Neuquén Group (taken and modified from Chiappe and Calvo, 1994, and Leanza et al., 2004) showing the diverse biota found in the outcrops of this formation mainly in the University Campus / localidad y horizonte. 1, mapa de Argentina y la región del Comahue señalando el sitio donde fueron recolectados los materiales de MUCPv-27; 2, columna estratigráfica de la Formación Bajo de la Carpa, Grupo Neuquén (tomado y modificado de Chiappe y Calvo, 1994, y Leanza et al., 2004) mostrando la variada biota ha- llada en los afloramientos de esta formación, especialmente en el campus universitario. AMEGHINIANA 47 (3), 2010 392 L.E. Fiorelli greatest damage in the presacral section is obser- tremely characteristic, with obvious sediment infi- ved ventrally, where the vertebrae lack their res- lling both perforations and cracks radiating from pective centra. Additionally, almost all neural them (figures 5.3, 5.6, 6.5). This clearly indicates that apophyses and neural spines are damaged at their the pressure exerted by the jaws of the predator on distal ends and several tiny bony fragments (figu- the caudal section was directed from outside to- res 3.1-3.3) were found during preparation. Diverse ward the center. Another important characteristic breakage marks and circular perforations filled by observed is that all perforations are arranged longi- sediment are present on the articulated dorsal pa- tudinally along the external surface of the tail (at le- ravertebral osteoderms (figures 3.1-3.3, 4.1-4.3). ast, three rows of punctures on each side of the tail). The perforations vary in diameter (~5-10 mm) and This supports the idea of a bite mark produced by a present a singular disposition. All perforations are predator that bit the tail multiple times. In addition, arranged linearly along the axis of the animal, in numerous caudal osteoderm fragments display bre- each osteoderm from the right side and located me- akage marks, which were posthumously filled by dial to the osteodermal keel (i.e., carina dermostea- sediment. Diverse caudal osteodrems were found lis) (figures 3.2, 4.2). In the corresponding preser- disarticulated, but associated with the tail; these ex- ved paravertebral osteoderms of the left side, the hibit considerable puncturing and breakage identi- same and very characteristic linear arrangement cal to that observed in the rest of the osteodrems (fi- can be observed (figure 3.1-3.3, 4.3). This alignment gure 6.4-6.7). of injuries along both sides of the trunk could indi- All caudal vertebrae and haemal arches remain cate a single bite made by larger predator on the articulated. Like the armor, these are extraordinarily back of MUCPv-27. well-preserved, although they have been affected by Diverse perforations and breakage marks can be predatory action too, a fact revealed by numerous bi- observed on the external surface of the articulated te marks observable throughout the series. For each osteoderms, suggesting that the perforations were bite mark, punctures and deeper breakage marks are made from the outside towards the inside. correlated with the breakage between the vertebrae- Moreover, the internal surface of some osteoderms mainly in the centra-and haemal arches (figures 5.1- displays unhealed bony elevations or incisions — 5.2, 6.1-6.3). The main breakage and punctures occu- and without fossilized connective tissue (figures rred in between the vertebrae, because the extremi- 5.3, 6.4-6.5)— underneath the external bite marks. ties of the vertebral centra are cracked (infillings of These traits cannot be observed on the right side os- sediment with small particles of bone; figure 6.3). teoderms. Breakage marks in the trunk osteoderms Moreover, the neural spines and apophyses present are also filled by sediment, indicating that the dor- considerable damage and breakage, because of co- sal section was covered with sediments subsequent llapse of the armor onto the axial skeleton possibly to the action of the predator. Such taphonomic fea- by the mandibular pressure exerted. tures suggest high fragmentation was produced by predation, before burial of the specimen. Some of the isolated osteoderms exhibit very sharp and acu- Discussion te punctures, as well as rounded and circular marks (figures 4.3, 5.2-5.3). The punctures and breakage displayed in the The tail section possesses dozens of bite marks, MUCPv-27 peirosaurid correspond clearly to bite injuries, perforations, punctures, breakage marks marks and injuries produced by a predator. Howe- and “scratches”. The circular and aligned bite ver, it cannot be determined whether the injuries marks are present on both sides of the tail (figures caused the death of the specimen or if they just re- 1.8, 5.1-5.7, 7.1-7.2). The articulated caudal region is present carrion biting. In any case, these two ideas crushed in a direction which is aligned with the are not mutually exclusive and a combination of both axes that join the ventral and dorsal bite marks. This cannot be rejected. The observed features however, suggests that the crushing of the caudal region may reject the hypothesis that the multiple bite marks and have been produced by one single bite delivered by injuries were the result of aggressive intraspecific the predator. Almost all the bony elements of the fights and/or agonistic social behavior including bi- tail show signs of damage, mainly in the armor (fi- ting related to rivalry between males (e.g., territoria- gures 1.8, 5.1-5.7, 6.1-6.3). The most important da- lity, reproduction, food). This conclusion is drawn mage is perforations directed from the outside to- from the fact that the bite marks and punctures are wards the inside of the armor plates. Most of these numerous (more than 70), producing considerable perforations are quite irregular on the osteoderm trauma to the organism. Crocodilian males normally external surface (range of diameter = 3-20 mm). use dominance advertisement postures and head- However, the corresponding internal marks are ex- slapping at the water surface (Garrick et al., 1978; AMEGHINIANA 47 (3), 2010 Predation on a Cretaceous peirosaurid crocodyliform 393 but the present specimen does not provide evidence of such behavior. Instead, bite marks found on MUCPv-27 suggest the attack of a significantly larger animal, able to inflict lethal wounds on this large-si- zed peirosaurid (~3-4 m in length).

Sedimentological and taphonomical considerations

Outcrops of the Bajo de la Carpa Formation at the University Campus quarry are composed of yellow quartzose sandstones, with poorly sorted subangular to subrounded grains, claystone matrix, calcareous cement, and light ferric color (Garrido, 2000). During the Santonian-Campanian, the Bajo de la Carpa For- mation biotope comprised a wide basin with fluvial Figure 4. Several isolated and articulated osteoderms of trunk of phases and extensive flood plains. This fluvial sys- MUCPv-27 with punctures and bite marks. 1, isolated osteoderm tem with very low sinuosity and abundant sand load fragments showing some punctures in dorsal view; 2, two articu- was also characterized by a complete absence of muds- lated paravertebral osteoderm plates from the right side of trunk tones (Garrido, 2000). Moreover, the arid and dry with aligned marks in dorsal view; 3, three paravertebral osteo- derm plates from the left side of trunk with circular aligned marks continental climate was dominated by aeolian depo- in ventral view. The black and white arrows indicate the puncture sition, creating large dunes and interdune lagoon ba- marks and injuries present in the specimen. Scale bars = 3 cm / al- sins skirted by fluvial deposits, crisscrossed by stre- gunos osteodermos del dorso de MUCPv-27 aislados y articulados con ams with the occurrence of seasonal flooding (Cald- perforaciones y marcas de mordidas. 1, vista dorsal de fragmentos de os- teodermos aislados que muestran perforaciones; 2, vista dorsal de dos os- well and Albino, 2001). teodermos paravertebrales articulados del sector derecho del tronco con Sánchez et al. (2006) characterized the sedimen- marcas alineadas; 3, vista ventral de tres osteodermos paravertebrales del tary and paleoenvironmental sequences of the out- lado izquierdo del tronco con marcas circulares alineadas. Las flechas ne- crops in the neighborhood of Neuquén city by means gras y blancas indican las marcas de mordeduras y heridas presentes en el espécimen/escala = 3 cm. of a very complete and detailed lithostratigraphic section of the Bajo de la Carpa Formation at the University Campus quarry. They determined that Vliet, 1989, 2001a, 2001b; Pough et al., 1998; Senter, this unit is represented —from base to top— by de- 2008) in intraspecific conflicts. However, there are posits of ephemeral fluvial systems followed by inte- eventually fights between males which cause some grated fluvio-aeolian systems. The former corres- damage, but rarely end in death of the animal (Cott, pond to canalized flows during maximum discharge 1961; Hunt, 1977). As was hypothesized by Avila et episodes, with fine- and medium-grained sandstones al. (2004), social behaviors observed in extant repre- rich in quartz and abundant yellow to pink silt—clay sentatives of the group were already present in more matrix. These sandstones are found as low angled basal crocodyliforms such as baurusuchids. This sug- cross beds. The fluvio-aeolian deposits were develo- gests that these behaviors appeared early in the evo- ped in a transverse dune field affected by ephemeral lutionary history of the group. According to Cott fluvial currents in the inter-dune areas, and parabolic (1961), in studies performed on specimens of the Nile dunes that were likely the result of remobilization of crocodile (Crocodylus niloticus Laurenti, 1768), the the underlying aeolian system, associated with perio- majority of injuries were produced by individuals of dic flood events by ephemeral sheet flows. These the same species —between rival males or attacks by beds appear as white sandstones with parallel and potential cannibals— and 70% of these occurred on horizontal lamination (Heredia and Calvo, 2002; the tail (Avila et al., 2004). These marks tend to be Sánchez et al., 2006). Moreover, these authors agree shallow and are unlikely to be fatal. that the extent and geometry of the dune fields res- Injuries inflicted on most postcranial elements of ponded to climatic variations of short term, fluvial specimen MUCPv-27 are not consistent with intras- system interference, and oscillations of phreatic le- pecific interactions such as recorded by Cott, (1961) vels, low sediment provision, and tectonic factors or Avilla et al. (2004), as they are much deeper and af- (Sánchez et al., 2006). fect both dorsal and caudal vertebrae. This does not In this unique environment, compared with other rule out the possibility that this species engaged in Patagonian Cretaceous settings, poor vegetation was intraspecific interactions involving non-lethal biting, influenced by a great seasonality, evidenced by the AMEGHINIANA 47 (3), 2010 394 L.E. Fiorelli

AMEGHINIANA 47 (3), 2010 Predation on a Cretaceous peirosaurid crocodyliform 395 discovery of abundant roots and bulbs. Also, insects crofragments, with sediment completely filling the and pupae chambers are very common (Caldwell spaces produced by the bite marks; this suggests the and Albino, 2001; Fiorelli et al., 2006). complete absence of selective transport. Despite the arid and relatively extreme conditions 3) The fact that the osteoderms remained articula- prevailing in the paleoenvironment of the University ted and imbricate in both dorsal and caudal sections Campus exposures during the Santonian, its taxono- is evidence that the remains were not eaten and that mic diversity was high (figure 2.2; see also Fauna of quick burial, but not transport, followed predation. the Bajo de la Carpa Formation section). The vertebrates On the other hand, several studies demonstrated from the University Campus area were found close that vertebrate predators and scavengers modify bo- to each other, in an area of approximately 40,000 m2 nes (e.g., Weigelt, 1989; Behrensmeyer, 1978; Hill, and representing mainly small- to medium-sized 1987; Njau and Blumenschine, 2006). The grooves (~0.3-2.0 m) specimens. The largest vertebrate remain found on fossil bones can best be attributed to dama- from this level is the peirosaurid specimen MUCPv- ge by a carnivorous animal since there is no reliable 27, with an estimated body length of 3-4 m. Other method to differentiate feeding during predation vertebrates are not larger than one or two meters, but versus scavenging (Barder et al., 2009). According to the bite marks on MUCPv-27 indicate the presence of Farlow and Holtz (2002), distinguishing successful a larger predatory species. predation events from scavenging on the basis of to- The general characteristic features exhibited by oth-marked bones is probably impossible, because the MUCPv-27 peirosaurid, reveal that the biostrati- the victim cannot recover from either. However, Bar- nomic processes were the most important taphono- der et al. (2009), Chure and Fiorillo (1997), Chure et al. mic processes. MUCPv-27 was exhumed in a quart- (1998), and Jacobsen (1999), among others, showed zite medium-grained sandstone matrix that is extre- that the grooves and repeated rectilinear striae on bo- mely friable and homogeneous. Although biostrati- nes in the fossil record were more probably produ- nomic attributes (i.e., climatic damage, breakage, ac- ced by vertebrate scavengers than active predators. cumulated abrasion, transport, predator/scavenger In this regard, the MUCPv-27 peirosaurid does not action) tend to increase with the time of sub-aerial ex- exhibit parallel grooves or rectilinear striae, indica- posure, the peirosaurid specimen MUCPv-27 exhi- ting that the carcass was not sub-aerially exposed for bits only bite marks and lacks other taphonomic at- a long time (which explains the lack of scavenging tributes. The damage produced by one or several events after predation). predators and the absence of other biostratinomic Disarticulation, breakage, fragmentation, and factors could indicate that the burial occurred shortly orientation of bones were therefore most likely gene- after the predation event (which might have produ- rated exclusively by predator action and not by phy- ced the death of this animal). Beyond the predation sical and/or weathering mechanics. The action of de- event, no important mechanical or physical transport composers produced no significant disarticulation took place before burial. This is inferred from three and dismemberment. Activities of arthropod or worm important key characteristics: scavenging, and fungal action are rejected or would 1) The articulated caudal section presents com- have been minimal due to the absence of any paleo- pression in a direction perpendicular to the longitu- sol and/or bioturbation in the bed where MUCPv-27 dinal tooth bite marks and to the inferred bite pres- was found. Therefore, bacterial action is considered sure (figure 7.1). For this reason, we can reject lithos- to be mainly responsible for necrolysis and decom- tatic forces or deformation/pressure by the sedi- position of the connective tissue after burial. Addi- ment. tionally, no bones exhibit bioerosion, accumulated 2) As described before, there are many bony mi- abrasion, bone surface deterioration or corrosion

Figure 5. MUCPv-27; several views of the articulated tail section showing many bite marks, perforations and injuries. 1, proximal sec- tion of tail in left lateral view (the fossil was found on its back with the ventral part facing upwards); 2, caudal vertebrae fully surroun- ded by caudal plates in left lateral view, showing the internal damage to the centra and neural spines; 3, row of right paravertebral cau- dal plates in inner view with tooth mark and punctures marks in both sides (observe the radial axes born from the central perforation in the left mark); 4, right accessory osteoderm plates of the tail showing numerous linearly arranged perforations; 5, middle section of the tail; 6, inner side of ventral plate of the middle section of tail with a clear puncture mark; 7, distal section of the tail in the left lateral view. White arrows indicate puncture marks and injuries / MUCPv-27; vistas de la sección caudal articulada mostrando numerosas mordedu- ras, perforaciones y lesiones. 1, vista lateral izquierda de la sección proximal de la cola (el fósil fue hallado invertido, con la parte ventral hacia arri- ba); 2, vista lateral izquierda de las vértebras caudales rodeadas completamente por osteodermos mostrando los daños internos en los centros y las es- pinas neurales; 3, vista interna de una hilera de osteodermos paravertebrales caudales del sector derecho con marcas de dientes y perforaciones en am- bos lados (obsérvense los ejes radiales que se extienden desde una de las perforaciones); 4, osteodermos accesorios derechos de la cola mostrando nu- merosas perforaciones alineadas; 5, sección media de la cola; 6, lado interno de un osteodermo ventral de la sección media de la cola mostrando una perforación muy clara; 7, vista lateral izquierda de la sección distal de la cola. Las flechas blancas muestran las perforaciones y lesiones. AMEGHINIANA 47 (3), 2010 396 L.E. Fiorelli

Figure 6. MUCPv-27, tail and osteodermal plates. 1 and 2, middle section of the tail of MUCPv-27 showing puncture and bite marks on the outside; 3, puncture marks and damage (arrows) in the inner side of the tail -mainly in the caudal vertebrae- when the osteodermal AMEGHINIANA 47 (3), 2010 Predation on a Cretaceous peirosaurid crocodyliform 397 mains— and numerous articulated or semi-articula- ted specimens with cranial remains of Notosuchus Woodward, 1896 and Dinilysia Woodward, 1901 (Caldwell and Albino, 2001; Albino and Caldwell, 2003; Pol, 2005; Fiorelli and Calvo, 2008). However, there is no case of preserved soft tissues (e.g., ten- dons, skin impressions), possibly because the typical quartzitic aeolian medium-grained sandstone from this stratigraphic level directly affects preservation. Taphonomic analysis indicates that the death of this peirosaurid was a selective event (due to preda- tion), and not caused by subsequent burial, because this represents a local catastrophic episode that also buried other representative vertebrates in the same unit at the University Campus quarry. Although not all the remains found in this quarry are contempora- neous, their taphonomic attributes are highly homo- geneous indicating little time averaging.

Figure 7. 1, Schematic reconstruction showing the articulated tail of MUCPv-27 as it was found in the sediment-turned up side The identity of the putative predator of MUCPv-27 down- and the injuries and bite pressure (black arrows) on both si- des; 2, restoration of the caudal section showing the correct posi- In the Bajo de la Carpa Formation, carrying one tion of tail and the several osteodermal plates completely enclo- of the richest and most characteristic vertebrate fau- sing the vertebrae. cv, caudal vertebra; ha: hemal arch; op, osteo- dermal plate / reconstrucción esquemática que muestra cómo fue halla- nas from the Neuquén Group, there are only two da en el sedimento la cola articulada de MUCPv-27 -con la superficie possible predatory or scavenging animals capable ventral girada hacia arriba- mostrando las lesiones y la presión de mordi- of producing such bite marks on a three meter long da (flechas negras) en ambos lados; 2, restauración de la sección caudal peirosaurid: a large crocodyliform or a theropod di- mostrando la correcta posición de la cola y la dermostea encerrando com- pletamente las vértebras. cv, vértebra caudal; ha, arco hemal; op, osteo- nosaur. Crocodyliforms dominated this fauna, in dermo. which the most conspicuous and abundant faunal element was the notosuchian Notosuchus terrestris Woodward, 1896 (more than 50 specimens found up (dissolution) signals. It is known that weathering in- to now). Although it represents a small- to medium- creases and bone density decreases with the distance sized form , recent studies on rostral, dental, cranial from the channel, so that in distal floodplain facies and postcranial features led to the conclusion that only scarce and weathered fossils occur (Behrensme- Notosuchus would have been an important herbivo- yer, 1978; Smith, 1993; Willis and Behrensmeyer, 1994; re, specializing in consumption of low-standing and Holz and Simões, 2005). In this regard, the sedimen- geophytic vegetation (Fiorelli et al., 2006; Fiorelli tary characteristic of the University Campus area and and Calvo, 2008). Nevertheless, a recent study on the homogeneous taphonomic attributes exhibited the teeth and dental characters of Notosuchus by MUCPv-27 suggest that this peirosaurid was ex- (Lecuona and Pol, 2008) showed differences in diet posed to weathering for only hours to a few days. type and feeding behavior among notosuchians (i.e., No other vertebrate remains found at the Univer- Sphagesaurus Price, 1950, and Mariliasuchus sity Campus quarry show significant transport featu- Carvalho and Bertini, 1999). Although no particular res, but in some cases some disarticulation or dis- diet has been inferred for Comahuesuchus brachybuc- memberment is present. The quarry yielded frequent calis Bonaparte, 1991, its cranial characteristics and and abundant in situ preserved avian egg-clutches small body size (Bonaparte, 1991; Martinelli, 2003) (Schweitzer et al., 2002) —some with embryonic re- make it obvious that it could not generate large bite

plates indicated in 1 and 2 are removed; 4 and 5, isolated fragments of dorsal and caudal osteodermal plates in external (4) and inner (5) views; 6 and 7, two articulated paravertebral caudal osteodermal plates from the left side in external (6) and inner (7) views. White arrows show puncture marks and injuries / MUCPv-27, cola y osteodermos 1 y 2, sección media de la cola de MUCPv-27 mostrando las perfo- raciones y mordeduras del lado externo; 3, perforaciones y daños (flechas) en el lado interno de la cola -principalmente en las vértebras caudales- cuan- do son removidos los osteodermos señalados en 1 y 2; 4 y 5 fragmentos aislados de osteodermos dorsales y caudales en vistas externa (4) e interna (5); 6 y 7, dos osteodermos paravertebrales caudales articulados del lado izquierdo en vistas externa (6) e interna (7). Las flechas blancas indican perfora- ciones y lesiones. AMEGHINIANA 47 (3), 2010 398 L.E. Fiorelli marks and cause great injuries. Overall, these typi- when they are neonates and juveniles (Scott, 2004). cal notosuchians can be rejected as potential preda- For that reason, predation marks on adult crocodi- tors of the peirosaurid under study. The basal me- lians are extremely rare, even more so in the fossil soeucrocodylian Neuquensuchus universitas Fiorelli record. Furthermore, although there have been clear and Calvo, 2007, represents a cursorial and running cases of predation and evidence of scavenging in the form of small to medium size. Although cranial re- fossil record (Erickson and Olson, 1996; Chure et al., mains are not known, Neuquensuchus probably had 1998; Frey et al., 2002; Everhart, 2005; Reisz and a small skull (~100-150 mm), with a morphology re- Tsuji, 2006; Bianucci et al., 2010; Hone et al., 2010), no sembling that of the skulls of Shantungosuchus recorded cases exist of predation and scavenging on Young, 1961, and Sichuanosuchus Peng, 1995 (Fio- terrestrial fossil crocodyliforms. Therefore, the pei- relli and Calvo, 2007), which disqualifies this cro- rosaurid specimen MUCP-27 represents the first ca- codyliform as another potential predator. Further se and demonstrates that large predators —other big crocodyliforms that coexisted with the peirosaurid crocodyliforms or maybe even theropod dino- specimen MUCP-27 are the baurusuchids Cyno- saurs— potentially chose other predators of conside- dontosuchus rothi Woodward, 1896, and Wargosuchus rable size as prey, such as this three meter long pei- australis Martinelli and Pais, 2008. These crocodyli- rosaurid. forms —in addition to other peirosaurids (perhaps with cannibalistic habits)— could possibly have be- en the predators or scavengers of specimen Acknowledgments MUCPv-27; they were macropredators and strict carnivores that inhabited the same semi-arid pa- I thank J. Calvo for access to the materials at the Comahue leoenvironment in what is now the University Cam- University Museum (MUC) to study the crocodyliforms under his care. I am indebted to D. Pol for his constant help and comments pus area of Neuquén city. However, the continuous on the peirosaurid specimen MUCPv-27, which were very useful longitudinal bite marks present in the caudal sec- for improving this work. I also express gratitude to P. Makovicky, tion indicate that the predator that made those D. Pol, and an anonymous referee for carefully reviewing, critici- marks had a large-sized skull. This observation zing and commenting. In addition, I thanks M.B. Andrade, D. Riff, A. Haro and M. Ezcurra, for their valuable comments and in-depth points further towards the possibility that a large review of the early manuscript. To R. Juárez Valieri for his help, in- theropod dinosaur was responsible for the bite formation, and comments. Thanks are also extensive to Sergio de marks in MUCPv-27. As previously mentioned, se- la Vega and Ivana Amelotti for their constant help. veral carnivorous dinosaurs are known from the Bajo de la Carpa Formation, although only some of them had large skulls, namely abelisaurids and car- References charodontosaurids (Porfiri and Calvo, 2006; Coria Albino, A.M. and Caldwell, M.W. 2003. Hábitos de vida de la ser- and Arcucci, 2004; Porfiri et al., 2008; Ezcurra and piente cretácica Dinilysia patagonica Woodward. Ameghiniana Méndez, 2009). The predator that caused the bites 40: 407-414. did not swallow the tail section after the attack, pos- Alvarenga, H. and Bonaparte, J.F. 1992. A new flightless landbird sibly because of the difficulty of tearing apart and from the Cretaceous of Patagonia. In: K.E. Campbell (ed.), Pa- pers in Avian Paleontology. Natural History Museum of Los swallowing this armored body part. This can be in- Angeles County, Science Series 36, pp. 51-64. ferred because the tail was not digested (the speci- Apesteguía, S. 2004. Bonitasaura salgadoi gen. et sp. nov.: a beaked men does not present abrasion, dissolution or bioe- sauropod from the Late Cretaceous of Patagonia. Naturwis- rosion), but instead remained articulated after the senschaften 91: 493-497. Avila, L.S., Fernandes, R. and Ramos, D.F.B. 2004. Bite marks on a generation of injuries and bite marks. crocodylomorph from the Upper Cretaceous of Brazil: evidence of social behavior? Journal of Vertebrate Paleontology 24: 971-973. Barder, K.S., Hasiotis, S.T. and Martin, L.D. 2009. Application of Conclusion forensic science techniques to trace fossils on dinosaur bones from a quarry in the Upper Jurassic Morrison Formation, Nor- theastern Wyoming. Palaios 24: 140-158. Although social behavior and ethological featu- Behrensmeyer, A.K. 1978. Taphonomic and ecologic information res of extant crocodyliforms are very complex (com- from bone weathering. Paleobiology 4: 150-162. bination of sensorial aspects, corporal postures and Bell, P.R., and Currie, P.J. 2009. A tyrannosaur jaw bitten by a con- familial: scavenging or fatal agonism? Lethaia 43: 278-281. social displays), it has been hypothesized that these Benson, R.B.J., Carrano, M.T. and Brusatte, S.L. 2009. A new clade characters were acquired early in the evolution of of archaic large-bodied predatory dinosaurs (Theropoda: Allo- the group (Avila et al., 2004). However, these com- sauroidea) that survived to the latest Mesozoic. Naturwissens- plex social behaviors rarely result in death but can chaften 97: 71-78. Bianucci, G., Sorce, B., Storai, T., and Landini, W. 2010. Killing in cause serious damage and harm in the individual. the Pliocene: shark attack on a dolphin from Italy. 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Mono- graph, Vol. 4: Monograph of the Science Museum of Min- nesota Paleontology, St. Paul, 38 pp. Schweitzer, M.H., Jackson, F.D., Chiappe, L.M., Schmitt, J.G., Calvo, J.O. and Rubilar, D.E. 2002. Late Cretaceous avian eggs with embryos from Argentina. Journal of Vertebrate Paleon- Recibido: 11 de mayo de 2009. tology 22: 191-195. Aceptado: 23 de abril de 2010.

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